Field of the Invention
The present invention relates to novel oil dispersion formulations (OD formulations) of iodosulfuron-methyl sodium salt which comprise hydroxystearates, in particular lithium hydroxystearate. Iodosulfuron-methyl sodium salt is a herbicidal active ingredient from the group of sulfonamides, in particular sulfonylureas.
Description of Related Art
Active ingredients for crop protection are generally not used in their pure form. Depending on the field of application and the type of application, and also on physical, chemical and biological parameters, the active ingredient is used in a mixture with customary auxiliaries and additives as active ingredient formulation. The combinations with other active ingredients for extending the spectrum of action and/or for protecting crop plants (e.g. by safeners, antidotes) are also known.
Formulations of active ingredients for crop protection should generally have high chemical and physical stability, good applicability and user friendliness and a broad biological effect with high selectivity.
Herbicidal active ingredients from the group of sulfonamides, such as sulfonylureas, generally have a high degree of chemical reactivity and tend towards chemical degradation, e.g. as a result of hydrolysis.
One option of formulating chemically labile active ingredients is the production of solid formulations. Thus, formulations of active ingredients from the group of sulfonylureas are known in the form of powders, granules and tablets (e.g. in EP A 764404, WO A 1998/34482, WO A 1993/13658). The processes for producing solid formulations, e.g. in the form of granules and tablets, however, are generally laborious, particularly if low-melting active ingredients or auxiliaries and additives are incorporated. Moreover, solid formulations are generally more difficult to apply and less user-friendly.
Liquid formulations are in most cases easier to apply, are more user-friendly and moreover generally exhibit better biological efficacy.
Liquid formulations of sulfonylureas are described e.g. in U.S. Pat. No. 4,599,412, U.S. Pat. No. 4,683,000, U.S. Pat. No. 4,671,817, EP A 245058, WO A 2001/82693, EP A 0313317, EP A 0514768, EP A 163598 and EP A 0514769.
The object of providing an improved crop protection composition formulation with the chemically very reactive sulfonylureas which has high chemical stability as well as high biological effectiveness and crop plant tolerability was described by the patent application WO A 2004/054364.
In addition, the use of sulfosuccinates as auxiliary is described in WO A 2004/054364. Sulfosuccinates are in the meantime used in most oil dispersion formulations of sulfonylureas and effect the chemical stabilization of the sulfonylureas.
Since the often used dioctylsulfosuccinate sodium salt has the classification R 41 (risk of serious damage to eyes) according to EU Guideline 67/548/EEC or 1999/45/EC, further, more user-friendly alternatives have been sought for the chemical stabilization of sulfonylureas.
Additionally, the oil dispersions are generally thickened with sheet silicates in order to prevent phase separations and settling of solid particles. The components hitherto used most frequently for this are the Bentone grades Bentone 34® and Bentone 38® from Elementis GmbH based on montmorillonite. However, these very frequently have a tendency toward uncontrolled considerable thickenings, which can make it difficult to empty the trade packs.
Moreover, the use of hydroxystearates as thickeners is known from the lubricant industry. A use of stearates in agrochemical formulations, however, has hitherto not been described.
It has now been found that when using hydroxystearates as thickeners in oil-based liquid formulations of iodosulfuron-methyl sodium salt the hydroxystearate surprisingly also brings about, as well as the thickening, a chemical stabilization of the sulfonylureas.
In particular, the lithium hydroxystearate exhibited a particularly significantly stabilizing effect on the sodium salt of iodosulfuron.